1. Field of the Invention
The invention relates to a cassette for an intraocular lens and also to an injection system for ejecting an intraocular lens from the cassette.
2. State of the Art
Nowadays, in cataract operations, an artificial lens, what is known as an intraocular lens (IOL), is implanted as standard into the capsular bag of the eye. During the operation, an ocular incision of from typically 2 to 4 mm is formed through which the natural eye lens is removed and replaced by the implant. In order to remove the natural eye lens, the natural eye lens is first destroyed by means of ultrasound and then extracted by suction. After removal of the natural eye lens, the artificial lens is introduced, in the folded state, through the incision into the capsular bag. As soon as the folded lens has been introduced into the capsular bag, the lens unfolds again into its original shape.
Improved operation tools and implants allow the surgeon to make the incisions smaller than in the past. Nowadays, the natural eye lens can be removed even through an incision of about 2 mm. However, this only makes sense if the intraocular lens can also be inserted through the same incision.
Cartridges, into which a lens can be loaded and then ejected out of the cartridge by means of an injector, have been developed in recent years for inserting an intraocular lens. Examples of cartridges and injectors of this type are known from American patents U.S. Pat. Nos. 4,681,102, 5,582,614, 5,947,975 and US patent application No. 2004/0199174.
In the injector device according to U.S. Pat. No. 4,681,102, the cartridge, which is embodied as a device for folding the lens, and the injector nozzle are separate parts. The cartridge can be inserted into the injector housing, whereupon the injector nozzle can be screwed at the front onto the injector housing.
In the injector device according to U.S. Pat. No. 5,582,614 and most previously known injector devices, the cartridge consists in one piece of a folding device and an injector nozzle.
US 2004/0199174 shows in FIG. 2 an injector device in which the injector housing consists in one piece of a cylinder for receiving the piston, a device for folding the lens and an injector nozzle.
The most commonly used intraocular lenses are made from a hydrophilic material. Lenses of this type are delivered in a liquid bath, packaged in a sterile manner by the manufacturer.
Storage in a liquid is necessary to prevent the lens from drying out. During the operation, the lens has to be removed from the packaging and inserted into the cartridge, whereupon this cartridge can then be loaded into the injector. As these are very small and resilient structures, there is a certain risk, during fitting of the cartridge, that the lens will fall out or jump away during folding and thus lose its stern y. This risk is particularly great in cartridges according to U.S. Pat. No. 4,681,102 which provides no measures for grasping the edges of the lens during folding.
US 2005/0049605 discloses an already loaded injection device with an injector body and an injector nozzle adjoining the injector body. The injector nozzle has, adjacent to the injector body, an aperture which serves to receive an IOL. The IOL is, in the unstressed state, held in the aperture by a mount which can be inserted from above. Mutually set-apart guide elements are molded laterally onto the aperture on one side of the aperture. The guide elements serve to receive a movable compression load which is displaceable perpendicularly to the longitudinal extension of the injection device. The compression load can be used to compress the IOL, once the mount has been removed, and to bring it into a state which is ready for injection. The injection device of US 2005/0049605 is already loaded by the manufacturer with an IOL and dispatched in a sterilized packaging. The advantage of the injection device of US 2005/0049605 is that the IOL is already inserted into the injection device and no longer has to be directly grasped by the surgeon. Nevertheless, a drawback of the injection device is that the device is suitable only for hydrophobic lenses, as the lens cannot be stored in liquid.
US 2007/0060925 discloses a system which also allows the preloading of hydrophilic lenses.
In this case, the system is divided into a distal and a proximal part. The distal part contains in this case the lens (IOL), the lens container and the cartridge and is sterilized and stored together in an additional, hermetically sealed container filled with liquid. Once the container has been opened, the distal and proximal parts have to be assembled by the operating staff.
Although mention is also made of the possibility of being able to sterilize the distal and proximal parts also in assembled form in a container (vial), this would require a very large container and a large amount of liquid. Drawbacks of this proposed solution include the fact that the liquid runs out when the container is opened. A system of this type would, on account of its size, also be awkward and not particularly customer-friendly.
A cassette and an injector for flexible intraocular lenses (IOLs) have become known through WO 03/049645. The cassette consists of a base part and a lid which is articulated to the base part. A hollow space, which serves to receive the lens, is formed in the lid and in the base part. An inlet opening and an outlet opening are provided at mutually opposing sides of the cassette. A plunger can be introduced into the cassette through the inlet opening in order to eject the lens through the outlet opening. Projections, which serve to interact with corresponding parts on the injector in order to precisely position the cassette in the injector, are provided on the base part and on the Hd. The cassette of WO 03/049645 is also suitable for receiving hydrophilic lenses. In this case, the cassette, with the lens received therein, is placed into a hermetically sealable container, which is filled with liquid, and sterilized in the container. Once the container has been opened by the operating staff, the cassette is inserted into the injector. Alternatively, it is proposed to mount the cassette already onto the injector and to hermetically seal the entire injector in the container which is filled with liquid. However, this again requires large containers; this is not user-friendly.
US 2002/0077633 discloses an implantation system for a deformable intraocular lens with an injector and a cassette. The cassette consists of a cassette lower part and a cassette upper part which, joined together, define space for receiving a lens. The cassette has at mutually opposing sides openings through which a piston of an injector can penetrate. A projection, which fits into a recess on the injector, is at the bottom of the cassette lower part. If the cassette is loaded into the injector, then the cassette is precisely positioned and the openings are coaxial with the displaceable piston.
All the cassettes described hereinbefore have in common the fact that the openings are not dosed for the passing of the injector piston and the issuing of the lens. The storage of lenses which have to be stored in liquid therefore necessitates in all cases a further container which is filled with liquid and in which the cassette can be stored in a hermetically sealed manner.
As described hereinbefore, cassettes in which hydrophilic IOLs are already preloaded are commercially available. The injector has, before the injector nozzle, an insertion receptacle into which the cassette is inserted. The cassette is removed from its container (wet packaging) with storage liquid and inserted into the injector. In order to prevent the IOL from slipping during the transfer in the cassette, the cassette is equipped with an interlocking device. As soon as the cassette is in the insertion device of the injector, the interlocking is broken off and the IOL is released for injection into the eye. The fact that the IOL is transferred to the injector in a cassette protecting the IOL is advantageous. Nevertheless, the drawback of the cassette is that it is very small and accordingly difficult to grasp using two fingers. A further drawback is that the IOL has direct contact with the environment, in the time from the removal of the packaging up to the fixing in the injector, via openings in the cassette which serve to introduce the injector piston and eject the IOL. Thus, accidental dropping of the cassette can render the IOL unusable.
It is therefore an advantage of the present invention to propose a cassette and an injector system comprising a cassette and injector that minimize the number of required manual interventions which are necessary during the surgical use of the IOL. A further advantage is to disclose means and ways as to how the lens, which is in particular stored in liquid, can be loaded into the device as early as during manufacture and remains securely positioned, after loading up to the operation, without the cassette, or even the entire injector, having in this case to be stored in an additional wet container.